Ink ribbon having an anisotropic electric conductivity

ABSTRACT

Polymeric ribbon having a plurality of chains of magnetized ferromagnetic conductive particles extending through the ribbon to yield an ink ribbon having an anisotropic electrical conductivity extending in the direction of the thickness of the ribbon.

United States Patent 11 1 Ehretsmann et a1.

[ INK RIBBON HAVING AN ANISOTROPIC ELECTRIC CONDUCTIVITY [75] Inventors: Jacques Ehretsmann,

Conches/Geneve; Emile Barbey, Geneve; Paul Heinzer, Zurich, all of Switzerland [73] Assignee: Battelle Memorial Institute;

Carouge/Geneva, Switzerland [22] Filed: Apr. 25, 1973 211 Appl. N6; 354,181

[30] Foreign Application Priority Data Apr. 26, 1972 Switzerland 1. 6235/72 .[52] US. Cl. 197/172, 117/238, 346/76 R [56] References Cited UNITED STATES PATENTS Speed 117/238 1 1 Nov. 12, 1974 l 2,917,996 12/1959 Epstein et a1. 346/76 R UX 3,001,891 9/1961 Stoller 117/238 3,117,065 l/1964 Woollen 1. 117/238 3,318,697 5/1967 Shrewshury 101/469 UX 3,441,940 4/1969 Salaman ct a1 346/76 R X 3,570,380 3/1971 Ktimenstein 1 197/1 R UX 3,588,912 6/1971 Hzickett 346/76 R 3,599,228 8/1971 Coco et a1 346/76 R OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Magnetic Transfer Medium, Miller et a1., Vol. 7, No. 6, Novemeber 1964, page 422.

Primary Examiner-Ernest T. Wright, Jr.

Attorney, Agent, or Firm-Hubbcll, Cohen & Stiefel [57] ABSTRACT 6 Claims, 4 Drawing Figures and electrically conducting.

INK RIBBON HAVING AN ANISOTROPIC ELECTRIC CONDUCTIVITY This invention relates to an ink ribbon having anisomechanism provided with an ink ribbon formed by a flexible supporthaving an electric conductivity which isgreater in the direction of its thickness than in the plane of its major surfaces, one surface of the support being coated with an ink which is both thermofusible The difference in conductivity of this ribbon is essentially due to the provision of a plurality of conductive elements in the mass of the ribbon, the conductive elements extending from one side to the other through'the thickness of the ribbon.

"With this ribbon the printing operation proper is effected-by locally pressing the inked surface of the ribbon against thesurfaceto be printed and each time connecting one or: more pairs of conductive elements to a first and a second terminal of a source of current for the first element and the second element of each pair, respectively, so that electriccurrent is fed through the portion of the 'ink layer between the two elements of each pair and. consequently this portion of the ink layer is melted by the Joule effect thus produced.

Such a ribbon has however some disadvantages both with respectto its production and its use. Among the disadvantages in use are the very stylized form of the obtained characters, the very limited number of possibilities in the choice of the lines produced with a group of given letters, and the difficulty of selectingthe electrodes from a group of electrodes occupying a very small surface on. the ribbon.

Therefore, it has been proposed in this French Patent to use a ribbon having an anisotropic electric conductivity in the direction of its thickness.

It is therefore an object of the present invention'to provide an :inkribbon havingananisotropic electric conductivity in the direction of its thickness and which ischaracterized in that it is formed of a resincontaining a plurality of chains of electrically conductive particles extending through the ribbon in'the direction of its thickness.

The accompanying drawing shows, schematically and merely by way of example, a preferred embodiment of means for producing the ribbon of the present invention according to different processes. In the drawing;

FIG. I is an elevational view of the ribbon producing means;

FIG. 52 is a sectional view taken on the line ll-ll of FIG. 1;

,FIG. 3 is a'transverse sectional view, taken on an enlarged scale,'through a mould for producing the ribbon; and

FIG-4 is .a perspective view, on an enlarged scale, of a piece of ribbon obtained by the process of'the present The prepolymer may be a Rhodester 1103 or a mixture of Rhodester 1103 and 1108. Rhodester 1103 is a prepolymer of polyester containing 45 percent of styrene. Its density at 25C. is I.06 before polymerization and H8 after polymerization. Its acid and hydroxyl values are both 10. Rhodester 1108 is a prepolymer of polyester containing 30 percent of styrene. Its density at 25C. is I.l4 before polymerization and l.23-after polymerization. Its acid value is 34 and its hydroxyl value is 42.

To prepare the mixture of nickel powder and Rhodester 1103 or the mixture of nickel powder and Rhodester 1103 and 1108, the nickel powder and the surfactant aredispersed in the prepolymer by subjecting the mixture to vibrations of a supersonic frequency. Then a catalyst is added to the mixture in a ratio of 0.3 percent to produce polymerization and an accelerator is added in a ratio of 0.l percent to accelerate the reactron.

This mixture is then spread in the form of a layer 1 *on a thin glass plate 2, as shown in FIG. 3. Previously spacer blocks 3 having a thickness of between 0.2 and 0.6 mm, depending on the thickness of the ribbon to be produced, are placed on the glass plate 2. Then a second glass plate 4 similar to the first one is placed on the blocks 3 to form a sandwich structure which is inserted in the airgap 5 of an electromagnet 6 formed by a coil '7 placedin a soft iron armature 8 having the form of an E in cross section. A cover 9 likewise of soft iron is placed on the armature 8, the cover 9 being provided with a longitudinal rib 9a facing the central rib 8a of the armature 8. The air gap 5 is located between the ribs 8a and 9a and has an elongateform, its dimensions being such that the aforementioned sandwich structure can be inserted therein.

After the sandwich structure has been placed into the airgap 5 the coil 7 is energized to produce a magnetic field in the air gap 5 so that the lines of force of the magnetic field traverse the sandwich structure. The magnetic field traversing the mixture 1 which is still in the liquid state produces an alignment of the nickel particles contained in the mixture 1 in the form of chains extending transversely in the direction of the thickness of the ribbon, i.e., along the lines of force of the magnetic field.

After this first form of carrying out the process of producing an anisotropic ink ribbon has thus been described, lets examine the influence of certain parameters on the anisotropic ribbonsproduced by means of the apparatus which so far has been summarily described. The results of these parameters and partieularly the resistivity of the ribbon in its transverse direcnym Qn t o a s ad ca e i t following Table i TABLE I Sample No. Nickel Type "/1 by Ribbon Magnetic field Transverse weight thickness Oe duratresistivity (a) ion in Ohm/cm hrs.

T 255 20 l00-200 2700 2.5 6 40a B20 40 30 ll0-l20 5800 l 0.8 40b SF 300 34 -90 3350 l 0.3

TABLE :..C9m .nq

Sample No. Nickel Type by Ribbon Magnetic field Transverse weight thickness e duratresistivity (,4) ion=in Ohm/cm hrs.

100120 5800 1 0.36 OSF l l0 OSF l0 42b 90-100 3350 l 0.4 44a B 20 40 50 5800 1 44b SF 300 60 110-120 335.0 1 0.36 45a B 20 40 50 110-120 2700 1 45b SF 300 60 100-110 1000 l 0.6

The origin and dimensions of the nickel powders mentioned in this table are indicated in the following Table 11.

The values of transverse resistivity given in ohm/cm in Table l are obtained by placing an electrode on each side of the ribbon and exerting a slight pressure on each.

of the electrodes and connecting the latter, for example, to an ohmmeter. in all the samples indicated in Table l the coefficient I of anisotropy given by the ratio between the resistance measured in a direction parallel to the surface of the ribbon and the resistance measured in a direction perpendicular to thissurface'is-higher than and thus excellent.

As will be seen by referring to Table 1, some of the indicated samples contain nickel powders of different origin and particle size which are indicated in Table 11.-

It has been found that this mixture of particles generally results in an improvement of the conductivity in the transverse direction of the ribbon, particularly when the medium diameter of the particles is different.

lt has also been found that the presence of large parti-' cles tends to produce a reduction in the resistivity of the ribbon. Further, by increasing the concentration of v the nickel powder'ribbons of better characteristics and the same good coefficients of anisotropy have been obtained. The orientation of the nickel particles by the mag netic field during the production of the ribbon takes place ratherrapidly, namely in the first 5 to 10 minutes. This is because after-this period the polymerization initiatedby the catalyst imparts to the prepolymer used as the starting material a viscosity which is so high that the.% nickel particles can no longer move under the influence of the lines of force of the magnetic field traversing the To form portion of the ribbon practically any type of plastics material may be used such asv heat-setting monomers, prepolymers, copolymers or polymers which initially are in the form-of a liquid hav ing a'sufficiently low viscosity to permit the orientation of the nickel particles under the influence of the magmust have certain plastic properties such as sufficient flexibility but low elasticity. I

To prepare the sample of the ribbon No. 22 of the Table l, a mixture of two prepolymers, the aforementioned Rhodester 1 103 and 1 108, has been used in the ratio of 7 to 3. For the samples of the ribbons No. 40 to 45 only Rhodester l 103 has been used. The mechanical properties of the polymer thus obtained are not as good as those of the polymer obtained by the mixture of Rhodester l 103 and 1 108 but the polymer made of Rhodester 1103 only has better properties of contact when an electrode is applied to the surface of the ribbon.

According to a second form of carrying out the process of producing an anisotropic ink ribbon, a thermoplastic or fusible resin is used which is heated to its melting point and then nickel powder is added to this resin by mixing it while the resin is in the molten state. Then this mixture is placed into a mould of the type lshown in FIG. 3, taking care that this mould has been heated previously -to a temperature corresponding to ithat of the melting point of the thermoplastic material employed, and then the mould is placed into the air gap .5 of the electromagnet 6 which is then energized to mlXtU16 while the mixture 18 cooling and hardening as was describedwith reference to the first form of carrying out the process.

According to a modification of this form of carrying out the processand if the speed of hardening of the resin is too high, small resistances may be arranged to lextend through the mould to keep the latter at a certain temperature and control the speed of lowering of the gt'emperature of the mixture;

Obviously this second form of carrying out the process may also be applied to a thermo-setting resin with :which nickel powder would be mixed. Then this mixture is placed into a mould such as that shown in FIG. 3, the mould is placed into the air gap 5 of the electro- :magnet 6 which is energized and simultaneously the mould is heated, for example, by means of electric resistances (not shown) extending through the mould, to harden the resin.

' FIG. 4 shows a piece of the ribbon 1 obtained by the 0 process described above and having an anisotropic electric conductivity. On the surface of this ribbon there can be seen the metal particles P to which an electrode can be applied and chains of particles C C C, appear on the side lb of the ribbon and form electrically conductive passages between the two surfaces -la and 1c of the ribbon.

iproduce an orientation of the metal particles of the in th in that said electrically conductive particles have a diameter between 2 and 50a.

4. An ink ribbon as claimed in claim 1, characterized at said resin is a polyester polymer.

5. An ink ribbon as claimed in claim 1, characterized in that said resin is a thermo-setting resin.

6. An ink ribbon as claimed in claim 1, characterized in that said resin is a thermoplastic resin.

Dedication 3,847,265.Jacques Ehretsmann, Conches/Geneve; Emile Barbey, Geneve and Paul Heinzer, Zurich, Switzerland. INK RIBBON HAVING AN AN- ISOTROPIC ELECTRIC CONDUCTIVITY. Patent dated Nov. 12, 1974. Dedication filed Mar. 26, 1984, by the assignee, Battelle Memorial Institute.

Hereby dedicates to the People of the United States the entire remaining term of said patent.

' [Oflicial Gazette May 29, 1984.]

Dedication 3,847,265.Jacques Ehretsmann, Conches/Geneve; Emile Barbey, Geneve and Paul Heinzer, Zurich, Switzerland. INK RIBBON HAVING AN AN- ISOTROPIC ELECTRIC CONDUCTIVIT Y. Patent dated Nov. 12,

1974. Dedication filed Mar. 26, 1984, by the assignee, Battelle Memorial Institute.

Hereby dedicates to the People of the United States the entire remaining term of said patent.

[Official Gazette May 29, 1984.] 

1. An ink ribbon having an anisotropic electric conductivity in the direction of the thickness of the ribbon, characterized in that said ribbon is formed of a resin containing a plurality of chains of electrically conductive particles extending through the ribbon in the direction of said thickness.
 2. An ink ribbon as claimed in claim 1, characterized in that said electrically conductive particles comprise a ferromagnetic metal.
 3. An ink ribbon as claimed in claim 1, characterized in that said electrically conductive particles have a diameter between 2 and 50 Mu .
 4. An ink ribbon as claimed in claim 1, characterized in that said resin is a polyester polymer.
 5. An ink ribbon as claimed in claim 1, characterized in that said resin is a thermo-setting resin.
 6. An ink ribbon as claimed in claim 1, characterized in that said resin is a thermoplastic resin. 